1. Field of the Invention
The present invention relates to an oil supply structure of a scroll compressor, and more particularly, to an oil supply structure of a scroll compressor that is capable of preventing a fine hole of an oil supply screw from being clogged with sludge.
2. Description of the Related Art
FIG. 1 is a longitudinal sectional view illustrating the interior configuration of a conventional scroll compressor.
As shown in FIG. 1, the conventional scroll compressor includes a shell 1, and main and sub flames 2 and 3 respectively arranged in the shell 1 at upper and lower portions of the shell 1. A stator 4 is mounted in the shell 1 between the main and sub frames 2 and 3. A rotor 5 is arranged inside the stator 4 such that it rotates when current flows through the stator 4.
A vertical crankshaft 6 is inserted and fixed through a central portion of the rotor 5 to rotate along with the rotor 5. The crankshaft 6 is rotatably supported at upper and lower ends thereof by the main and sub frames 2 and 3.
An orbiting scroll 7 is mounted to an upper surface of the main frame 2 in the shell 1. The orbiting scroll 7 is coupled at a lower portion thereof with the crankshaft 6, and is provided at an upper portion thereof with an orbiting wrap 7a having an involuted shape. A fixed scroll 8 is arranged on the orbiting scroll 7 in the shell 1 while being fixed to the shell 1. The fixed scroll 8 is provided with a fixed wrap 8a adapted to be engaged with the orbiting wrap 7a of the orbiting scroll 7 such that compression chambers 21 are defined between the wraps 7a and 8a. With this configuration, when the orbiting scroll 7 performs an orbiting motion in accordance with rotation of the crankshaft 6, gaseous refrigerant is introduced into the compression chambers 21 to be compressed.
To couple the orbiting scroll 7 to the crankshaft 6, the crankshaft 6 is provided with a crank pin 10 upwardly protruded from the upper end of the crankshaft 6 at a position radially spaced apart from the center of the upper end of the crankshaft 6 by a certain distance. Also, the orbiting scroll 7 is provided, at the lower portion thereof, with a boss 7b centrally protruded from a lower surface of the orbiting scroll 7. A bearing 11 is forcibly fitted into the boss 7b. Also, an eccentric bush 12 is rotatably fitted around the crank pin 10. The crank pin 10 of the crankshaft 6 is inserted into the boss 7b of the orbiting scroll 7 via the bearing 11 and eccentric bush 12, so that the orbiting scroll 7 is coupled to the crankshaft 6.
As a rotation preventing mechanism for the orbiting scroll 7, an Oldham ring 9 is arranged between the main frame 2 and the orbiting scroll 7. An oil passage 6a is vertically perforated through the crankshaft 6. Upper and lower balance weight members 13 and 14 are provided at upper and lower surfaces of the rotor 5, respectively, in order to prevent rotational unbalance of the crankshaft 6 caused by the crank pin 10.
As the high-pressure gaseous refrigerant, which is compressed in the compression chambers, is discharged through a discharge port 17 of the fixed scroll 8, it applies shock to a top cap 1 a of the shell 1 to thereby generate noise. For this reason, a muffler 22, having a cap shape, is arranged on the fixed scroll 8 to attenuate the noise.
In addition to the noise attenuation function as stated above, when the muffler 22 is employed in a high-pressure scroll compressor in which the high-pressure gaseous refrigerant is discharged to a lower portion of the compressor, the muffler 22 also serves to separate a low-pressure region, that is affected by a suction pressure, from a high-pressure region that is affected by a discharge pressure. The fixed scroll 8 is provided with a passage guide 23 in order to guide the compressed gaseous refrigerant inside the muffler 22 to the lower portion of the compressor.
In FIG. 1, reference numerals 15 and 16 designate suction and discharge pipes, respectively, reference numeral 18 designates a discharge chamber, reference numeral 19 designates oil, and reference numeral 20 designates an oil propeller.
When current flows through the stator 4, the rotor 5 is rotated inside the stator 4, thereby causing the crankshaft 6 to rotate. In accordance with the rotation of the crankshaft 6, the orbiting scroll 7 coupled to the crank pin 10 of the crankshaft 6 performs an orbiting motion with an orbiting radius defined between the center of the crankshaft 6 and the center of the orbiting scroll 7.
In accordance with a continued orbiting motion of the orbiting scroll 7, the compression chambers 21, which are defined between the orbiting wrap 7a and the fixed wrap 8a, are gradually reduced in volume, so that gaseous refrigerant sucked into each compression chamber 21 is compressed to high pressure. The compressed high-pressure gaseous refrigerant is subsequently discharged into the discharge chamber 18 via the discharge port 17. The compressed high-pressure gaseous refrigerant is then directed to the lower portion of the compressor via the passage guide 23 of the fixed scroll 8 to thereby be discharged to the outside via the discharge pipe 16.
FIG. 2 is a partially enlarged sectional view of FIG. 1.
As shown in FIG. 2, the main frame 2 is provided with an oil supply screw 24. If oil is fed into a backpressure space C1, that is defined between the orbiting scroll 7 and the main frame 2, via the crankshaft 6 in accordance with operation of the compressor, the oil supply screw 24 supplies the oil from the backpressure space C1 into a space C2 that is defined between the fixed scroll 8 and the main frame 2. Here, the backpressure space C1 forms a high-pressure chamber, and the space C2 forms a low-pressure chamber.
FIG. 3 is a perspective view illustrating a cut-away half section of the oil supply screw of FIG. 2.
As shown in FIG. 3, the oil supply screw 24 has a stepped screw body 25 having upper and lower portions of different diameters. The screw body 25 is externally formed with threads 26 to be screwed into a screw bore 2a of the main frame 2.
An orifice 27 is perforated through a central portion of the screw body 25. The orifice 27 includes a center hole 28 formed at the upper portion of the screw body 25, and a fine hole 29 formed at the lower portion of the screw body 25 to communicate with the center hole 28. The fine hole 29 has a smaller diameter than the center hole 28 and is centered about the center hole 28. With such a configuration, the orifice 27 is able to achieve the appropriate supply of oil while eliminating the interference of the discharge pressure.
However, the oil supply screw of the conventional scroll compressor has a problem in that the diameter of the fine hole of the orifice is extremely small and an entrance end of the oil supply screw has an even structure. This causes various foreign matter and sludge contained in the oil to be accumulated at the entrance end of the oil supply screw to thereby be introduced into the fine hole.
As a result, the fine hole of the oil supply screw is clogged with the various foreign matter and sludge contained in the oil, making it impossible to supply an appropriate amount of oil to a compression unit, and consequently degrading performance and reliability of the scroll compressor.